Interaction of B lymphocyte Signal Transduction-Associated Adaptor Protein Bam32 with Hic-5

The B lymphocyte adaptor molecule of 32 kD(Bam 32) acts as conduicts to channel upstream signals into downstream effectors branches.To explore the role of Bam32 in B cell antigen receptor (BCR) signaling,an yeast two_hybrid screening the library from fetal mouse was performed to identify molecules that could interact with Bam32. One of the positive clones was found to encode Hic-5, a member of the paxillin protein family. It has been proved that paxillin plays a critical role in the signal transduction pathways of integrin, a receptor involving in many important functions such as adhesion of cell to extracellular matrix, cell movement etc. Through co-transfection of 293T cells with expression plasmids and immunoprecipitation, this study confirmed that Hic-5 could precipitate together with Bam32, suggesting their interaction inside mammalian cells. By using specific anti-phosphotyrosine antibody, it was found that both Bam32 and Hic-5 could be phosphorylated by Lyn, a protein tyrosine kinase. The results indicated that the interaction of Bam32 with Hic-5 might play an important role in activating downstream signaling molecules and in the regulation of cell adhesion and movement.